Amplification systems and methods with one or more channels

ABSTRACT

Systems and methods are provided for amplifying multiple input signals to generate multiple output signals. An example system includes a first channel, a second channel, and a third channel. The first channel is configured to receive one or more first input signals, process information associated with the one or more first input signals and a first ramp signal, and generate one or more first output signals. The second channel is configured to receive one or more second input signals, process information associated with the one or more second input signals and a second ramp signal, and generate one or more second output signals. The first ramp signal corresponds to a first phase. The second ramp signal corresponds to a second phase. The first phase and the second phase are different.

1. CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201310368267.1, filed Aug. 21, 2013, commonly assigned, incorporated byreference herein for all purposes.

2. BACKGROUND OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides amplification systems and methodswith one or more channels. Merely by way of example, the invention hasbeen applied to a Class-D amplifier. But it would be recognized that theinvention has a much broader range of applicability.

FIG. 1 is a simplified conventional diagram showing an amplificationsystem using a Class-D amplifier with one channel. The amplificationsystem 100 includes a modulator 102, an output stage 104, a low-passfilter 106, and an output load 116. The modulator 102 includes anoscillator 108, a comparator 110 and a loop filter 112. For example, theoutput load 116 is a speaker. In another example, the modulator 102, theoutput stage 104, and the low-pass filter 106 are included in a Class-Damplifier. In yet another example, the low-pass filter 106 includes oneor more inductors and/or one or more capacitors. In yet another example,the low-pass filter 106 includes one or more bead cores and/or one ormore capacitors.

The loop filter 112 receives an input audio signal 118 and an outputsignal 120 (e.g., a pulse-width-modulation signal) and outputs afiltered signal 122 to the comparator 110. For example, the input audiosignal 118 includes a pair of input signals. The oscillator 108generates a clock signal 126 and a ramp signal 124 which is received bythe comparator 110. The comparator 110 outputs a comparison signal 128that indicates a comparison between the ramp signal 124 and the filteredsignal 122. The output stage 104 receives the comparison signal 128 andgenerates the output signal 120. The low-pass filter 106 converts theoutput signal 120 to an audio signal 130 to drive the load 116. As shownin FIG. 1, one channel including the modulator 102 and the output stage104 is implemented. Multiple channels may be used foraudio-amplification applications.

In one embodiment, the loop filter 112 amplifies an error signal betweenthe input signal 118 and a feedback signal associated with the outputsignal 120. For example, the loop filter 112 includes a low pass filterwhich has a very high gain (e.g., a high gain larger than 1000) in a lowfrequency range and a very low gain (e.g., a low gain much smallerthan 1) in a high frequency range. In another example, if a signalincludes a low-frequency component and a high-frequency component, theloop filter 112 amplifies the low-frequency component with a high gainand amplifies the high-frequency component with a low gain (e.g., a lowgain much smaller than 1). In yet another example, if the high-frequencycomponent is close to a switching frequency of the amplification system100, the loop filter 112 attenuates the high-frequency component. In oneembodiment, the loop filter 112 includes one or more stages of analogintegrators.

FIG. 2 is a simplified conventional diagram for an amplification systemwith multiple channels. The amplification system 300 includes multiplechannels 202 ₁, . . . , 202 _(n), . . . , 202 _(N), where N≥2 and 1≤n≤N.The first channel 202 ₁ includes a loop filter 204 ₁, comparators 206 ₁and 208 ₁, a logic controller 210 ₁, driving components 212 ₁ and 214 ₁,transistors 216 ₁, 218 ₁, 220 ₁ and 222 ₁, and a low-pass filter 224 ₁.The logic controller 210 ₁ includes one or more buffers. For example,the low-pass filter 224 ₁ includes one or more inductors and/or one ormore capacitors. In another example, the low-pass filter 224 ₁ includesone or more bead cores and/or one or more capacitors. Other channelshave similar components as the first channel. As shown in FIG. 2, thesechannels 202 ₁, . . . , 202 _(n), . . . , 202 _(N) share a common rampsignal 228 and generate output signals (e.g., 234 ₁, . . . , 234 _(n), .. . , 234 _(N) and/or 236 ₁, . . . , 236 _(n), . . . , 236 _(N)) so thataudio signals are provided to output loads 222 ₁, . . . , 222 _(n), . .. , 222 _(N) (e.g., speakers) respectively.

In one embodiment, the loop filter 204 ₁ amplifies the error signalbetween an input differential signal and a feedback differential signalassociated with an output differential signal. The input differentialsignal represents a difference between the input signals 230 ₁ and 232₁, and the output differential signal represents a difference betweenthe output signals 234 ₁ and 236 ₁. For example, the loop filter 204 ₁is a low pass filter and it has a very high gain (e.g., a high gain thatis greater than 1000) in a low frequency range and a very low gain(e.g., a low gain that is much smaller than 1) in a high frequencyrange. In another example, if a signal includes a low-frequencycomponent and a high-frequency component, the loop filter 204 ₁amplifies the low-frequency component with a high gain and amplifies thehigh-frequency component with a low gain (e.g., a low gain that is muchsmaller than 1). In yet another example, if the high-frequency componentis close to a switching frequency of the amplification system 200, theloop filter 204 ₁ attenuates the high-frequency component. In oneembodiment, the loop filter 204 ₁ includes one or more stages of analogintegrators. In some embodiments, loop filters in other channels are thesame as the loop filter 204 ₁.

The amplification systems 100 and 200 often have certain disadvantages.Hence it is highly desirable to improve such amplification systems.

3. BRIEF SUMMARY OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides amplification systems and methodswith one or more channels. Merely by way of example, the invention hasbeen applied to a Class-D amplifier. But it would be recognized that theinvention has a much broader range of applicability.

According to one embodiment, a system for amplifying multiple inputsignals to generate multiple output signals includes a first channel, asecond channel, and a third channel. The first channel is configured toreceive one or more first input signals, process information associatedwith the one or more first input signals and a first ramp signal, andgenerate one or more first output signals based on at least informationassociated with the one or more first input signals and the first rampsignal. The second channel is configured to receive one or more secondinput signals, process information associated with the one or moresecond input signals and a second ramp signal, and generate one or moresecond output signals based on at least information associated with theone or more second input signals and the second ramp signal. The thirdchannel is configured to receive one or more third input signals,process information associated with the one or more third input signalsand a third ramp signal, and generate one or more third output signalsbased on at least information associated with the one or more thirdinput signals and the third ramp signal. The first ramp signalcorresponds to a first phase. The second ramp signal corresponds to asecond phase. The first phase and the second phase are different.

According to another embodiment, a system for amplifying multiple inputsignals to generate multiple output signals includes a first channel anda second channel. The first channel is configured to receive one or morefirst input signals, process information associated with the one or morefirst input signals and a first ramp signal, and generate one or morefirst output signals based on at least information associated with theone or more first input signals and the first ramp signal. The secondchannel is configured to receive one or more second input signals,process information associated with the one or more second input signalsand a second ramp signal, and generate one or more second output signalsbased on at least information associated with the one or more secondinput signals and the second ramp signal. The first ramp signalcorresponds to a first phase. The second ramp signal corresponds to asecond phase. A difference between the first phase and the second phaseis equal to 180 degrees.

According to yet another embodiment, a system for amplifying multipleinput signals to generate multiple output signals includes a firstchannel and a second channel. The first channel includes a first loopfilter, a first signal processing component and a first outputcomponent, and is configured to receive one or more first input signals,process information associated with the one or more first input signalsand a ramp signal, and generate one or more first output signals basedon at least information associated with the one or more first inputsignals and the ramp signal. The second channel includes a second loopfilter, a second signal processing component and a second outputcomponent, and is configured to receive one or more second inputsignals, process information associated with the one or more secondinput signals and the ramp signal, and generate one or more secondoutput signals based on at least information associated with the one ormore second input signals and the ramp signal. The first loop filter isconfigured to process information associated with the one or more firstinput signals and generate one or more first filtered signals based onat least information associated with the one or more first inputsignals. The first signal processing component is configured to processinformation associated with the one or more first filtered signals andgenerate one or more first processed signals based on at leastinformation associated with the one or more first filtered signals. Thefirst output component is configured to process information associatedwith the one or more first processed signals and generate the one ormore first output signals based on at least information associate withthe one or more first processed signals. The second loop filter isconfigured to process the one or more second input signals and generateone or more second filtered signals based on at least informationassociated with the one or more second input signals. The second signalprocessing component is configured to process information associatedwith the one or more second filtered signals and generate one or moresecond processed signals based on at least information associated withthe one or more second filtered signals. The second output component isconfigured to process information associated with the one or more secondprocessed signals and generate the one or more second output signalsbased on at least information associate with the one or more secondprocessed signals. The one or more first processed signals areassociated with a first phase. The one or more second processed signalsare associated with a second phase. A difference between the first phaseand the second phase is equal to 180 degrees.

In one embodiment, a system for amplifying multiple input signals togenerate multiple output signals includes a first channel and a secondchannel. The first channel includes a first loop filter and one or morefirst comparators, and is configured to receive one or more first inputsignals, process information associated with the one or more first inputsignals and a ramp signal, and generate one or more first output signalsbased on at least information associated with the one or more firstinput signals and the ramp signal. The second channel includes a secondloop filter and one or more second comparators, and is configured toreceive one or more second input signals, process information associatedwith the one or more second input signals and the ramp signal, andgenerate one or more second output signals based on at least informationassociated with the one or more second input signals and the rampsignal. The first loop filter is configured to process informationassociated with the one or more first input signals and generate one ormore first filtered signals based on at least information associatedwith the one or more first input signals. The one or more firstcomparators include one or more first terminals and one or more secondterminals and are configured to receive the one or more first filteredsignals at the first terminals and the ramp signal at the secondterminals, generate one or more first comparison signals based on atleast information associated with the first filtered signals and theramp signal, and output the one or more first comparison signals inorder to generate the one or more first output signals. The second loopfilter is configured to process information associated with the one ormore second input signals and generate one or more second filteredsignals based on at least information associated with the one or moresecond input signals. The one or more second comparators include one ormore third terminals and one or more fourth terminals and are configuredto receive the one or more second filtered signals at the thirdterminals and the ramp signal at the fourth terminals, generate one ormore second comparison signals based on at least information associatedwith the second filtered signals and the ramp signal, and output the oneor more second comparison signals in order to generate the one or moresecond output signals. The one or more second terminals include one ormore inverting terminals and the one or more fourth terminals includeone or more non-inverting terminals, or the one or more second terminalsinclude one or more non-inverting terminals and the one or more fourthterminals include one or more inverting terminals.

In another embodiment, a system for amplifying one or more input signalsto generate one or more output signals includes, an oscillator componentconfigured to generate a ramp signal associated with a rampingfrequency, a loop filter component configured to receive one or moreinput signals and generate one or more filtered signals based on atleast information associated with the one or more input signals, and acomparator component configured to receive the one or more filteredsignals and the ramp signal and generate one or more comparison signalsbased on at least information associated with the one or more filteredsignals and the ramp signal. The oscillator component is furtherconfigured to, change the ramping frequency periodically so that one ormore changes in the ramping frequency are made in each jittering periodcorresponding to a jittering frequency, and output the ramping signalassociated with the changed ramping frequency. The jittering frequencyis larger than an upper limit of a predetermined audio frequency range.

In yet another embodiment, a system for amplifying one or more inputsignals to generate one or more output signals includes, an oscillatorcomponent configured to generate a ramp signal associated with a rampingfrequency, the ramping frequency corresponding to one or more rampingperiods, a loop filter component configured to receive one or more inputsignals and generate one or more filtered signals based on at leastinformation associated with the one or more input signals, and acomparator component configured to receive the one or more filteredsignals and the ramp signal and generate one or more comparison signalsbased on at least information associated with the one or more filteredsignals and the ramp signal. The oscillator component is furtherconfigured to, at an end of a first ramping period, change a chargingcurrent or a discharging current so that a first duration of the firstramping period differs from a second duration of a second ramping periodfollowing the first ramping period. The first duration and the secondduration correspond to different magnitudes of the ramping frequency.

According one embodiment, a method for amplifying multiple input signalsto generate multiple output signals includes, receiving one or morefirst input signals, processing information associated with the one ormore first input signals and a first ramp signal, and generating one ormore first output signals based on at least information associated withthe one or more first input signals and the first ramp signal. Themethod further includes, receiving one or more second input signals,processing information associated with the one or more second inputsignals and a second ramp signal, and generating one or more secondoutput signals based on at least information associated with the one ormore second input signals and the second ramp signal. In addition, themethod includes receiving one or more third input signals, processinginformation associated with the one or more third input signals and athird ramp signal, and generating one or more third output signals basedon at least information associated with the one or more third inputsignals and the third ramp signal. The first ramp signal corresponds toa first phase. The second ramp signal corresponds to a second phase. Thefirst phase and the second phase are different.

According to another embodiment, a method for amplifying multiple inputsignals to generate multiple output signals includes, receiving one ormore first input signals, processing information associated with the oneor more first input signals and a first ramp signal, and generating oneor more first output signals based on at least information associatedwith the one or more first input signals and the first ramp signal. Themethod further includes, receiving one or more second input signals,processing information associated with the one or more second inputsignals and a second ramp signal, and generating one or more secondoutput signals based on at least information associated with the one ormore second input signals and the second ramp signal. The first rampsignal corresponds to a first phase. The second ramp signal correspondsto a second phase. A difference between the first phase and the secondphase is equal to 180 degrees.

According to yet another embodiment, a method for amplifying multipleinput signals to generate multiple output signals includes, receivingone or more first input signals by a first channel including a firstloop filter, a first signal processing component and a first outputcomponent, processing information associated with the one or more firstinput signals and a ramp signal, and generating one or more first outputsignals based on at least information associated with the one or morefirst input signals and the ramp signal. The method further includes,receiving one or more second input signals by a second channel includinga second loop filter, a second signal processing component and a secondoutput component, processing information associated with the one or moresecond input signals and the ramp signal, and generating one or moresecond output signals based on at least information associated with theone or more second input signals and the ramp signal. The processinginformation associated with the one or more first input signals and aramp signal includes, processing information associated with the one ormore first input signals by the first loop filter, generating one ormore first filtered signals based on at least information associatedwith the one or more first input signals, processing informationassociated with the one or more first filtered signals by the firstsignal processing component, and generating one or more first processedsignals based on at least information associated with the one or morefirst filtered signals. The generating one or more first output signalsbased on at least information associated with the one or more firstinput signals and the ramp signal includes, processing informationassociated with the one or more first processed signals by the firstoutput component, and generating the one or more first output signalsbased on at least information associate with the one or more firstprocessed signals. The processing information associated with the one ormore second input signals and the ramp signal includes, processinginformation associated with the one or more second input signals by thesecond loop filter, generating one or more second filtered signals basedon at least information associated with the one or more second inputsignals, processing information associated with the one or more secondfiltered signals by the second signal processing component, andgenerating one or more second processed signals based on at leastinformation associated with the one or more second filtered signals. Thegenerating one or more second output signals based on at leastinformation associated with the one or more second input signals and theramp signal includes, processing information associated with the one ormore second processed signals by the second output component, andgenerating the one or more second output signals based on at leastinformation associate with the one or more second processed signals. Theone or more first processed signals are associated with a first phase,the one or more second processed signals are associated with a secondphase, and a difference between the first phase and the second phase isequal to 180 degrees.

In one embodiment, a method for amplifying multiple input signals togenerate multiple output signals includes, receiving one or more firstinput signals by a first channel including a first loop filter and oneor more first comparators, processing information associated with theone or more first input signals and a ramp signal, and generating one ormore first output signals based on at least information associated withthe one or more first input signals and the ramp signal. The methodfurther includes, receiving one or more second input signals by a secondchannel including a second loop filter and one or more secondcomparators, processing information associated with the one or moresecond input signals and the ramp signal, and generating one or moresecond output signals based on at least information associated with theone or more second input signals and the ramp signal. The processinginformation associated with the one or more first input signals and aramp signal includes, processing information associated with the one ormore first input signals at the first loop filter, and generating one ormore first filtered signals based on at least information associatedwith the one or more first input signals. The generating one or morefirst output signals based on at least information associated with theone or more first input signals and the ramp signal includes, receivingthe one or more first filtered signals by one or more first terminals ofthe one or more first comparators, receiving the ramp signal by one ormore second terminals of the one or more first comparators, generatingone or more first comparison signals based on at least informationassociated with the first filtered signals and the ramp signal,outputting the one or more first comparison signals, and generating theone or more first output signals based on at least informationassociated with the one or more first comparison signals. The processinginformation associated with the one or more second input signals and theramp signal includes, processing information associated with the one ormore second input signals by the second loop filter, and generating oneor more second filtered signals based on at least information associatedwith the one or more second input signals. The generating one or moresecond output signals based on at least information associated with theone or more second input signals and the ramp signal includes, receivingthe one or more second filtered signals by one or more third terminalsof the one or more second comparators, receiving the ramp signal by oneor more fourth terminals of the one or more second comparators,generating one or more second comparison signals based on at leastinformation associated with the second filtered signals and the rampsignal, outputting the one or more second comparison signals, andgenerating the one or more second output signals based on at leastinformation associated with the one or more second comparison signals.The one or more second terminals include one or more inverting terminalsand the one or more fourth terminals include one or more non-invertingterminals, or the one or more second terminals include one or morenon-inverting terminals and the one or more fourth terminals include oneor more inverting terminals.

In another embodiment, a method for amplifying one or more input signalsto generate one or more output signals includes, generating a rampsignal associated with a ramping frequency, receiving one or more inputsignals, and processing information associated with the one or moreinput signals. The method further includes, generating one or morefiltered signals based on at least information associated with the oneor more input signals, receiving the one or more filtered signals andthe ramp signal, processing information associated with the one or morefiltered signals and the ramp signal, and generating one or morecomparison signals based on at least information associated with the oneor more filtered signals and the ramp signal. The generating a rampsignal associated with a ramping frequency includes, changing theramping frequency periodically so that one or more changes in theramping frequency are made in each jittering period corresponding to ajittering frequency, and outputting the ramping signal associated withthe changed ramping frequency. The jittering frequency is larger than anupper limit of a predetermined audio frequency range.

In yet another embodiment, a method for amplifying one or more inputsignals to generate one or more output signals includes, generating aramp signal associated with a ramping frequency, the ramping frequencycorresponding to one or more ramping periods, receiving one or moreinput signals, and processing information associated with the one ormore input signals. The method further includes, generating one or morefiltered signals based on at least information associated with the oneor more input signals, receiving the one or more filtered signals andthe ramp signal, and generating one or more comparison signals based onat least information associated with the one or more filtered signalsand the ramp signal. The generating a ramp signal associated with aramping frequency includes changing a charging current or a dischargingcurrent at an end of a first ramping period so that a first duration ofthe first ramping period differs from a second duration of a secondramping period following the first ramping period. The first durationand the second duration correspond to different magnitudes of theramping frequency.

Depending upon embodiment, one or more benefits may be achieved. Thesebenefits and various additional objects, features and advantages of thepresent invention can be fully appreciated with reference to thedetailed description and accompanying drawings that follow.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified conventional diagram showing an amplificationsystem using a Class-D amplifier with one channel.

FIG. 2 is a simplified conventional diagram for an amplification systemwith multiple channels.

FIG. 3 is a simplified diagram for an amplification system with multiplechannels according to an embodiment of the present invention.

FIG. 4 is a simplified timing diagram for the amplification system asshown in FIG. 3 according to an embodiment of the present invention.

FIG. 5(a) is a simplified diagram showing an amplification system withtwo channels according to an embodiment of the present invention.

FIG. 5(b) is a simplified diagram showing an amplification system withtwo channels according to another embodiment of the present invention.

FIG. 5(c) is a simplified diagram showing an amplification system withtwo channels according to yet another embodiment of the presentinvention.

FIG. 6 is a simplified diagram for an amplification system according toan embodiment of the present invention.

FIG. 7 is a simplified timing diagram for the oscillator with periodicjittering as part of the amplification system as shown in FIG. 6according to an embodiment of the present invention.

FIG. 8(a) is a simplified diagram showing certain components of theoscillator with periodic jittering as part of the amplification systemas shown in FIG. 6 according to one embodiment of the present invention.

FIG. 8(b) is a simplified timing diagram for the oscillator as shown inFIG. 8(a) as part of an amplification system according to one embodimentof the present invention.

FIG. 8(c) is a simplified diagram showing certain components of theoscillator with periodic jittering as part of the amplification systemas shown in FIG. 6 according to another embodiment of the presentinvention.

FIG. 9 is a simplified timing diagram for the amplification system asshown in FIG. 6 that includes an oscillator with periodic jittering andreceives one or more input signals according to one embodiment of thepresent invention.

FIG. 10 is a simplified timing diagram showing a combination of periodicjittering and pseudo-random jittering for the oscillator as part of theamplification system as shown in FIG. 6 according to yet anotherembodiment of the present invention.

FIG. 11 is a simplified frequency diagram for the amplification systemas shown in FIG. 6 that includes an oscillator with a combination ofperiodic jittering and pseudo-random jittering if the input signal iszero according to one embodiment of the present invention.

FIG. 12(a) is a simplified diagram showing certain components of theoscillator with a combination of periodic jittering and pseudo-randomjittering as part of the amplification system as shown in FIG. 6according to one embodiment of the present invention.

FIG. 12(b) is a simplified diagram showing certain components of theoscillator with a combination of periodic jittering and pseudo-randomjittering as part of the amplification system as shown in FIG. 6according to another embodiment of the present invention.

5. DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides amplification systems and methodswith one or more channels. Merely by way of example, the invention hasbeen applied to a Class-D amplifier. But it would be recognized that theinvention has a much broader range of applicability.

Referring to FIG. 2, as multiple channels receive a common ramp signal,the output signals (e.g., 234 ₁, . . . , 234 _(n), . . . , 234 _(N)and/or 236 ₁, . . . , 236 _(n), . . . , 236 _(N)) may be of a samefrequency and have a same phase. That is, all power stages may be turnedon and off at approximately the same time, which often causes a largeripple for the power supply that is applied to the amplification system200.

FIG. 3 is a simplified diagram for an amplification system with multiplechannels according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The amplification system300 includes multiple channels 302 ₁, . . . , 302 _(n), . . . , 302_(N), where N≥2 and 1≤n≤N.

As an example, the first channel 302 ₁ includes a loop filter 304 ₁,comparators 306 ₁ and 308 ₁, a logic controller 310 ₁, drivingcomponents 312 ₁ and 314 ₁, transistors 316 ₁, 318 ₁, 320 ₁ and 322 ₁,and a low-pass filter 324 ₁. Other channels have similar components asthe first channel, according to certain embodiments. For example, thetransistors 316 ₁, 318 ₁, 320 ₁, and 322 ₁ are N-channel transistors. Asan example, the logic controller 310 ₁ includes one or more buffers. Inanother example, the low-pass filter 3241 includes one or more inductorsand/or one or more capacitors. In yet another example, the low-passfilter 324 ₁ includes one or more bead cores and/or one or morecapacitors. In one embodiment, the loop filter 304 ₁ amplifies the errorsignal between an input differential signal and a feedback differentialsignal associated with an output differential signal. The inputdifferential signal represents a difference between the input signals332 ₁ and 330 ₁, and the output differential signal represents adifference between the output signals 334 ₁ and 336 ₁. For example, theloop filter 304 ₁ includes a low pass filter which has a very high gain(e.g., a high gain larger than 1000) in a low frequency range and a verylow gain (e.g., a low gain much smaller than 1) in a high frequencyrange. In another example, if a signal includes a low-frequencycomponent and a high-frequency component, the loop filter 304 ₁amplifies the low-frequency component with a high gain and amplifies thehigh-frequency component with a low gain (e.g., a low gain much smallerthan 1). In yet another example, if the high-frequency component isclose to a switching frequency of the amplification system 300, the loopfilter 304 ₁ attenuates the high-frequency component. In one embodiment,the loop filter 304 ₁ includes one or more stages of analog integrators.

According to some embodiments, ramp signals (e.g., 328 ₁, . . . , 328_(N)) received by different channels have a same frequency but differentphases. In one embodiment, the phase shifts between the ramps signalsreceived by different channels are equal. As an example, the firstchannel 302 ₁ receives the ramp signal 328 ₁ for processing inputsignals 330 ₁ and 332 ₁. In another embodiment, the second channel 302 ₂(not shown in FIG. 3) receives a ramp signal 328 ₂ and the phase shiftbetween the ramp signal 328 ₂ and the ramp signal 328 ₁ is

$\frac{2\pi}{N},$

the phase shift between a ramp signal 328 ₃ received by the thirdchannel 302 ₃ (not shown in FIG. 3) and the ramp signal 328 ₁ is

$\frac{4\pi}{N},$

and the phase shift between the ramp signal 328 _(N) received by thelast channel 302 _(N) and the ramp signal 328 ₁ is

$\frac{2\pi \times \left( {N - 1} \right)}{N}.$

In yet another embodiment, the phase shifts between the ramps signalsreceived by different channels are different. As an example, the phaseshift between the first channel 302 ₁ and the second channel 302 ₂ isdifferent from the phase shift between the second channel 302 ₂ and thethird channel 302 ₃.

FIG. 4 is a simplified timing diagram for the amplification system 300according to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The waveform 402 ₁represents the ramp signal 328 ₁ as a function of time, the waveform 402₂ represents the ramp signal 328 ₂ as a function of time, the waveform402 ₃ represents the ramp signal 328 ₃ as a function of time, and thewaveform 402 _(N) represent the ramp signal 328 _(N) as a function oftime. As shown in FIG. 4, the phase shift between the ramp signal 328 ₁and the ramp signal 328 ₂ is φ₁, the phase shift between the ramp signal328 ₂ and the ramp signal 328 ₃ is φ′, and the phase shift between theramp signal 328 ₁ and the ramp signal 328 _(N) is φ_(N), according tocertain embodiments. For example, the phase shift φ₁ is equal to ordifferent from the phase shift φ′.

FIG. 5(a) is a simplified diagram showing an amplification system withtwo channels according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The amplification system500 includes loop filters 502 and 504, comparators 506, 508, 510 and512, logic controllers 514 and 516, driving components 518, 520, 522 and524, transistors 526, 528, 530, 532, 534, 536, 538 and 540, and low-passfilters 542 and 544. For example, the amplification system 500 is theamplification system 300 with N equals to 2.

In one embodiment, the loop filter 502, the comparators 506 and 508, thelogic controller 514, the driving components 518 and 520, thetransistors 526, 528, 530 and 532, and the low-pass filter 542 areincluded in a first channel. In another embodiment, the loop filter 504,the comparators 510 and 512, the logic controller 516, the drivingcomponents 522 and 524, the transistors 534, 536, 538 and 540, and thelow-pass filter 544 are included in a second channel. The logiccontroller 514 includes two buffers 550 and 552, and the logiccontroller 516 includes two buffers 554 and 556. In some embodiments,the transistors 526, 528, 530, 532, 534, 536, 538 and 540 are N-channeltransistors, for example, N-channel metal-oxide-semiconductor fieldeffect transistors (MOSFETs). In certain embodiments, the transistors526, 530, 534 and 538 are P-channel transistors (e.g., P-channelMOSFETs), and the transistors 528, 532, 536, and 540 are N-channeltransistors (e.g., N-channel MOSFETs). As an example, the low-passfilters 542 and 544 each include one or more inductors and/or one ormore capacitors. In another example, the low-pass filters 542 and 544each include one or more bead cores and/or one or more capacitors.

In yet another example, the loop filter 502, the comparators 506 and508, the logic controller 514, the driving components 518 and 520, thetransistors 526, 528, 530 and 532, and the low-pass filter 542 are thesame as the loop filter 304 ₁, the comparators 306 ₁ and 308 ₁, thelogic controller 310 ₁, the driving components 312 ₁ and 314 ₁, thetransistors 316 ₁, 318 ₁, 320 ₁ and 322 ₁, and the low-pass filter 324₁, respectively. In yet another example, the loop filter 504, thecomparators 510 and 512, the logic controller 516, the drivingcomponents 522 and 524, the transistors 534, 536, 538 and 540, and thelow-pass filter 544 are the same as the loop filter 304 ₁, thecomparators 306 ₁ and 308 ₁, the logic controller 310 ₁, the drivingcomponents 312 ₁ and 314 ₁, the transistors 316 ₁, 318 ₁, 320 ₁ and 322₁, and the low-pass filter 324 ₁, respectively.

According to one embodiment, the first channel receives input signals560 and 562 and a ramp signal 568 and generates output signals 572 and574 to provide one or more audio signals 580 to an output load 546(e.g., a speaker). Specifically, for example, the loop filter 502receives the input signals 560 and 562 and generates filtered signals584 and 586 which are received by the comparators 506 and 508,respectively. As an example, the comparators 506 and 508 also receivethe ramp signal 568 and generate comparison signals 588 and 590,respectively. The logic controller 514 outputs signals 596 and 598 tothe driving components 518 and 520, respectively. For example, the loopfilter 502 receives the output signals 572 and 574 as feedbacks. In oneexample, if the comparison signal 588 is at a logic high level, thesignal 596 is at the logic high level, and if the comparison signal 588is at a logic low level, the signal 596 is at the logic low level. Inanother example, if the comparison signal 590 is at the logic highlevel, the signal 598 is at the logic high level, and if the comparisonsignal 590 is at the logic low level, the signal 598 is at the logic lowlevel.

According to another embodiment, the second channel receives inputsignals 564 and 566 and a ramp signal 570 and generates output signals576 and 578 to provide one or more audio signals 582 to an output load548 (e.g., a speaker). Specifically, for example, the loop filter 504receives the input signals 564 and 566 and generates filtered signals588 and 590 which are received by the comparators 510 and 512,respectively. As an example, the comparators 510 and 512 also receivethe ramp signal 570 and generate comparison signals 592 and 594,respectively. The logic controller 516 outputs signals 597 and 599 tothe driving components 522 and 524, respectively. For example, the loopfilter 504 receives the output signals 576 and 578 as feedbacks. In oneexample, if the comparison signal 592 is at the logic high level, thesignal 597 is at the logic high level, and if the comparison signal 592is at the logic low level, the signal 597 is at the logic low level. Inanother example, if the comparison signal 594 is at the logic highlevel, the signal 599 is at the logic high level, and if the comparisonsignal 594 is at the logic low level, the signal 599 is at the logic lowlevel.

As an example, the ramp signals 568 and 570 are of the same frequency,and the phase shift between the ramp signal 568 and the ramp signal 570is π (e.g., 180°). That is, the ramp signal 568 is out of phase with theramp signal 570.

In one embodiment, the loop filter 502 amplifies the error signalbetween an input differential signal and a feedback differential signalassociated with an output differential signal. The input differentialsignal represents a difference between the input signals 560 and 562,and the output differential signal represents a difference between theoutput signals 572 and 574. For example, the loop filter 502 is a lowpass filter and it has a very high gain (e.g., a high gain that isgreater than 1000) in a low frequency range and a very low gain (e.g., alow gain that is much smaller than 1) in a high frequency range. Inanother example, if a signal includes a low-frequency component and ahigh-frequency component, the loop filter 502 amplifies thelow-frequency component with a high gain and amplifies thehigh-frequency component with a low gain (e.g., a low gain that is muchsmaller than 1). In yet another example, if the high-frequency componentis close to a switching frequency of the amplification system 500, theloop filter 502 attenuates the high-frequency component. In oneembodiment, the loop filter 502 includes one or more stages of analogintegrators. In some embodiments, the loop filter 504 is the same as theloop filter 502.

FIG. 5(b) is a simplified diagram showing an amplification system withtwo channels according to another embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. The amplificationsystem 600 includes loop filters 602 and 604, comparators 606, 608, 610and 612, logic controllers 614 and 616, driving components 618, 620, 622and 624, transistors 626, 628, 630, 632, 634, 636, 638 and 640, andlow-pass filters 642 and 644.

In one embodiment, the loop filter 602, the comparators 606 and 608, thelogic controller 614, the driving components 618 and 620, thetransistors 626, 628, 630 and 632, and the low-pass filter 642 areincluded in a first channel. In another embodiment, the loop filter 604,the comparators 610 and 612, the logic controller 616, the drivingcomponents 622 and 624, the transistors 634, 636, 638 and 640, and thelow-pass filter 644 are included in a second channel. The logiccontroller 614 includes two buffers 650 and 652, and the logiccontroller 616 includes two NOT gates 654 and 656. In some embodiments,the transistors 626, 628, 630, 632, 634, 636, 638 and 640 are N-channeltransistors, for example, N-channel MOSFETs. In certain embodiments, thetransistors 626, 630, 634 and 638 are P-channel transistors (e.g.,P-channel MOSFETs), and the transistors 628, 632, 636, and 640 areN-channel transistors (e.g., N-channel MOSFETs). As an example, thelow-pass filters 642 and 644 each include one or more inductors and/orone or more capacitors. In another example, the low-pass filters 642 and644 each include one or more bead cores and/or one or more capacitors.In yet another example, the loop filter 602, the comparators 606 and608, the logic controller 614, the driving components 618 and 620, thetransistors 626, 628, 630 and 632, and the low-pass filter 642 are thesame as the loop filter 304 ₁, the comparators 306 ₁ and 308 ₁, thelogic controller 310 ₁, the driving components 312 ₁ and 314 ₁, thetransistors 316 ₁, 318 ₁, 320 ₁ and 322 ₁, and the low-pass filter 324₁, respectively. In yet another example, the loop filter 604, and thecomparators 610 and 612 are the same as the loop filter 304 ₁, thecomparators 306 ₁ and 308 ₁, respectively.

According to one embodiment, the first channel receives input signals660 and 662 and a ramp signal 668 and generates output signals 672 and674 to provide one or more audio signals 680 to an output load 646(e.g., a speaker). Specifically, for example, the loop filter 602receives the input signals 660 and 662 and the output signals 672 and674 as feedbacks, and generates filtered signals 684 and 686 which arereceived by the comparators 606 and 608, respectively. As an example,the comparators 606 and 608 also receive the ramp signal 668 andgenerate comparison signals 688 and 690, respectively. The logiccontroller 614 outputs signals 696 and 698 to the driving components 618and 620, respectively. For example, if the comparison signal 688 is at alogic high level, the signal 696 is at the logic high level, and if thecomparison signal 688 is at a logic low level, the signal 696 is at thelogic low level. In another example, if the comparison signal 690 is atthe logic high level, the signal 698 is at the logic high level, and ifthe comparison signal 690 is at the logic low level, the signal 698 isat the logic low level. In certain embodiments, the logic controller 614is removed, and the signals 688 and 690 are the same as the signals 696and 698, respectively. For example, the comparators 606, 608, 610 and612 each receive the ramp signal 668 at a non-inverting terminal (e.g.,a “+” terminal). In another example, the comparators 606, 608, 610 and612 each receive the ramp signal 668 at an inverting terminal (e.g., a“−” terminal).

According to another embodiment, the second channel receives inputsignals 664 and 666 and the ramp signal 668 and generates output signals676 and 678 to provide one or more audio signals 682 to an output load648 (e.g., a speaker). Specifically, for example, the loop filter 604receives the input signals 664 and 666 and the output signals 676 and678 as feedbacks, and generates filtered signals 688 and 690 which arereceived by the comparators 610 and 612, respectively. As an example,the comparators 610 and 612 also receive the ramp signal 668 andgenerate comparison signals 692 and 694, respectively. The logiccontroller 616 outputs signals 697 and 699 to the driving components 622and 624, respectively. For example, if the comparison signal 692 is atthe logic high level, the signal 697 is at the logic low level, and ifthe comparison signal 694 is at the logic low level, the signal 697 isat the logic high level. In another example, if the comparison signal694 is at the logic high level, the signal 699 is at the logic lowlevel, and if the comparison signal 694 is at the logic low level, thesignal 699 is at the logic high level. In yet another example, thecomparators 606 receives the signal 684 at an inverting terminal (e.g.,a “−” terminal); the comparators 608 receives the signal 686 at aninverting terminal (e.g., a “−” terminal); the comparators 610 receivesthe signal 688 at an inverting terminal (e.g., a “−” terminal); and thecomparators 612 receives the signal 690 at an inverting terminal (e.g.,a “−” terminal).

In one embodiment, the loop filter 602 amplifies the error signalbetween an input differential signal and a feedback differential signalassociated with an output differential signal. The input differentialsignal represents a difference between the input signals 660 and 662,and the output differential signal represents a difference between theoutput signals 672 and 674. For example, the loop filter 602 is a lowpass filter and it has a very high gain (e.g., a high gain that isgreater than 1000) in a low frequency range and a very low gain (e.g., alow gain that is much smaller than 1) in a high frequency range. Inanother example, if a signal includes a low-frequency component and ahigh-frequency component, the loop filter 602 amplifies thelow-frequency component with a high gain and amplifies thehigh-frequency component with a low gain (e.g., a low gain that is muchsmaller than 1). In yet another example, if the high-frequency componentis close to a switching frequency of the amplification system 600, theloop filter 602 attenuates the high-frequency component. In oneembodiment, the loop filter 602 includes one or more stages of analogintegrators. In some embodiments, the loop filter 604 is the same as theloop filter 602.

FIG. 5(c) is a simplified diagram showing an amplification system withtwo channels according to yet another embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. Theamplification system 1600 includes loop filters 1602 and 1604,comparators 1606, 1608, 1610 and 1612, logic controllers 1614 and 1616,driving components 1618, 1620, 1622 and 1624, transistors 1626, 1628,1630, 1632, 1634, 1636, 1638 and 1640, and low-pass filters 1642 and1644.

In one embodiment, the loop filter 1602, the comparators 1606 and 1608,the logic controller 1614, the driving components 1618 and 1620, thetransistors 1626, 1628, 1630 and 1632, and the low-pass filter 1642 areincluded in a first channel. In another embodiment, the loop filter1604, the comparators 1610 and 1612, the logic controller 1616, thedriving components 1622 and 1624, the transistors 1634, 1636, 1638 and1640, and the low-pass filter 1644 are included in a second channel. Thelogic controller 1614 includes two buffers 1650 and 1652, and the logiccontroller 1616 includes two buffers 1654 and 1656. In some embodiments,the transistors 1626, 1628, 1630, 1632, 1634, 1636, 1638 and 1640 areN-channel transistors, for example, N-channel MOSFETs. In certainembodiments, the transistors 1626, 1630, 1634 and 1638 are P-channeltransistors (e.g., P-channel MOSFETs), and the transistors 1628, 1632,1636, and 1640 are N-channel transistors (e.g., N-channel MOSFETs). Asan example, the low-pass filters 1642 and 1644 each include one or moreinductors and/or one or more capacitors. In another example, thelow-pass filters 1642 and 1644 each include one or more bead coresand/or one or more capacitors. In yet another example, the loop filter1602, the comparators 1606 and 1608, the logic controller 1614, thedriving components 1618 and 1620, the transistors 1626, 1628, 1630 and1632, and the low-pass filter 1642 are the same as the loop filter 304₁, the comparators 306 ₁ and 308 ₁, the logic controller 310 ₁, thedriving components 312 ₁ and 314 ₁, the transistors 316 ₁, 318 ₁, 320 ₁and 322 ₁, and the low-pass filter 324 ₁, respectively. In yet anotherexample, the loop filter 1604, and the comparators 1610 and 1612 are thesame as the loop filter 304 ₁, the comparators 306 ₁ and 308 ₁,respectively.

According to one embodiment, the first channel receives input signals1660 and 1662 and a ramp signal 1668 and generates output signals 1672and 1674 to provide one or more audio signals 1680 to an output load1646 (e.g., a speaker). Specifically, for example, the loop filter 1602receives the input signals 1660 and 1662 and the output signals 1672 and1674 as feedbacks, and generates filtered signals 1684 and 1686 whichare received by the comparators 1606 and 1608, respectively. As anexample, the comparators 1606 and 1608 also receive the ramp signal 1668and generate comparison signals 1688 and 1690, respectively. The logiccontroller 1614 outputs signals 1696 and 1698 to the driving components1618 and 1620, respectively. For example, if the comparison signal 1688is at a logic high level, the signal 1696 is at the logic high level,and if the comparison signal 1688 is at a logic low level, the signal1696 is at the logic low level. In another example, if the comparisonsignal 1690 is at the logic high level, the signal 1698 is at the logichigh level, and if the comparison signal 1690 is at the logic low level,the signal 1698 is at the logic low level. In certain embodiments, thelogic controller 1614 is removed, and the signals 1688 and 1690 are thesame as the signals 1696 and 1698, respectively. In some embodiments,the logic controller 1616 is removed, and the signals 1692 and 1694 arethe same as the signals 1697 and 1699, respectively. For example, thecomparators 1610 and 1612 each receive the ramp signal 1668 at anon-inverting terminal (e.g., a “+” terminal), and the comparators 1606and 1608 each receive the ramp signal 1668 at an inverting terminal(e.g., a “−” terminal).

According to another embodiment, the second channel receives inputsignals 1664 and 1666 and the ramp signal 1668 and generates outputsignals 1676 and 1678 to provide one or more audio signals 1682 to anoutput load 1648 (e.g., a speaker). Specifically, for example, the loopfilter 1604 receives the input signals 1664 and 1666 and the outputsignals 1676 and 1678 as feedbacks, and generates filtered signals 1688and 1690 which are received by the comparators 1610 and 1612,respectively. As an example, the comparators 1610 and 1612 also receivethe ramp signal 1668 and generate comparison signals 1692 and 1694,respectively. In another example, the logic controller 1616 outputssignals 1697 and 1699 to the driving components 1622 and 1624,respectively. In yet another example, the comparators 1606 receives thesignal 1684 at a non-inverting terminal (e.g., a “+” terminal); thecomparators 1608 receives the signal 1686 at a non-inverting terminal(e.g., a “+” terminal); the comparators 1610 receives the signal 1688 atan inverting terminal (e.g., a “−” terminal); and the comparators 1612receives the signal 1690 at an inverting terminal (e.g., a “−”terminal).

In one embodiment, the loop filter 1602 amplifies the error signalbetween an input differential signal and a feedback differential signalassociated with an output differential signal. The input differentialsignal represents a difference between the input signals 1660 and 1662,and the output differential signal represents a difference between theoutput signals 1672 and 1674. For example, the loop filter 1602 is a lowpass filter and it has a very high gain (e.g., a high gain that isgreater than 1000) in a low frequency range and a very low gain (e.g., alow gain that is much smaller than 1) in a high frequency range. Inanother example, if a signal includes a low-frequency component and ahigh-frequency component, the loop filter 1602 amplifies thelow-frequency component with a high gain and amplifies thehigh-frequency component with a low gain (e.g., a low gain that is muchsmaller than 1). In yet another example, if the high-frequency componentis close to a switching frequency of the amplification system 1600, theloop filter 1602 attenuates the high-frequency component. In oneembodiment, the loop filter 1602 includes one or more stages of analogintegrators. In some embodiments, the loop filter 1604 is the same asthe loop filter 1602.

As discussed above and further emphasized here, FIG. 3, FIG. 5(a), FIG.5(b) and FIG. 5(c) are merely examples, which should not unduly limitthe scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. For example,the phase shift between the ramp signals 568 and 570 is not equal to π.In another example, the channels 302 ₁, . . . , 302 _(N) each include aseparate oscillator for generating the ramp signals 328 ₁, . . . , 328_(N), respectively. In yet another example, the channels 302 ₁, . . . ,302 _(N) share a common oscillator which generates the ramp signals 328₁, . . . , 328 _(N). In yet another example, the two channels as shownin FIG. 5(a) each include a separate oscillator for generating the rampsignals 568 and 570, respectively. In yet another example, the twochannels as shown in FIG. 5(a) share a common oscillator which generatesthe ramp signals 568 and 570.

Referring back to FIG. 2, the amplification system 200 often involves ahigh switching frequency, and electromagnetic interference issues may beimportant.

FIG. 6 is a simplified diagram for an amplification system according toan embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. The amplification system 800 includes a modulator802, an output stage 804, a low-pass filter 806, and an output load 816.The modulator 802 includes a loop filter 812, an oscillator 808, and acomparator 810. For example, the output load 816 is a speaker. Inanother example, the low pass filter 806 includes one or more inductorsand/or one or more capacitors. In yet another example, the low-passfilter 806 includes one or more bead cores and/or one or morecapacitors. In yet another example, the modulator 802, the output stage804, and the low-pass filter 806 are included in a Class-D amplifier.

According to one embodiment, the loop filter 812 receives an input audiosignal 818 and outputs a filtered signal 822 to the comparator 810. Forexample, the input audio signal 818 includes a pair of input signals. Inanother example, the oscillator 808 generates a clock signal 826 and aramp signal 824. As an example, the comparator 810 receives the rampsignal 824 and provides a comparison signal 828 to the output stage 804which generates an output signal 820. In one example, the loop filter812 receives the output signal 820 as a feedback. For example, thelow-pass filter 806 converts the output signal 820 to an audio signal830 to drive the load 816. As shown in FIG. 6, the modulator 802, theoutput stage 804 and the low-pass filter 806 may be included in onechannel of a multi-channel amplification system, according to certainembodiments. For example, the output signal 820 includes one or moresignals. In another example, the output signal 820 represents adifference between two signals.

According to another embodiment, the oscillator 808 is configured toprovide periodic jittering to the oscillation frequency of the clocksignal 826 and/or the ramping frequency of the ramp signal 824. Forexample, the oscillation frequency of the clock signal 826 and/or theramping frequency of the ramp signal 824 vary in a particular range inresponse to the periodic jittering. In another example, the frequency(e.g., a repeat rate) of the periodical jittering is larger than anupper limit of an audio frequency range (e.g., of about 20 Hz to about20 KHz). In yet another example, the oscillation frequency of the clocksignal 826 is equal to the ramping frequency of the ramp signal 824.

According to yet another embodiment, the oscillator 808 is configured toprovide a combination of the periodic jittering and pseudo-randomjittering to the oscillation frequency of the clock signal 826 and/orthe ramping frequency of the ramp signal 824. For example, theoscillation frequency of the clock signal 826 and/or the rampingfrequency of the ramp signal 824 varies in a particular range inresponse to the combination of the periodic jittering and pseudo-randomjittering. In another example, the frequency (e.g., a repeat rate) ofthe pseudo-random jittering is smaller than a lower limit of an audiofrequency range (e.g., of about 20 Hz to about 20 KHz).

According to yet another embodiment, the ramp signal 824 is associatedwith one or more ramping periods which are related to the rampingfrequency of the ramp signal 824. For example, the oscillator 808 isconfigured to adjust the ramp signal 824 in a first ramping period toaffect a slope of the ramp signal 824 in a next ramping period and/orthe duration of the next ramping period. Specifically, the oscillator808 is configured to change a ramp-up slope and/or a ramp-down slopeassociated with the ramp signal 824 (e.g., in a periodic manner or in apseudo-random manner), in some embodiments. According to certainembodiments, the amplification system 800 as shown in FIG. 6 can beimplemented in one or more channels as shown in FIG. 3, FIG. 5(a),and/or FIG. 5(b) to further improve the one or more channels. Forexample, periodic jittering or a combination of periodic jittering andpseudo-random jittering is provided to the one or more channels thatimplement an amplification system similar to the amplification system800.

In one embodiment, the loop filter 812 amplifies an error signal betweenthe input signal 818 and a feedback signal associated with the outputsignal 820. For example, the loop filter 812 includes a low pass filterwhich has a very high gain (e.g., a high gain larger than 1000) in a lowfrequency range and a very low gain (e.g., a low gain much smallerthan 1) in a high frequency range. In another example, if a signalincludes a low-frequency component and a high-frequency component, theloop filter 812 amplifies the low-frequency component with a high gainand amplifies the high-frequency component with a low gain (e.g., a lowgain much smaller than 1). In yet another example, if the high-frequencycomponent is close to a switching frequency of the amplification system800, the loop filter 812 attenuates the high-frequency component. In oneembodiment, the loop filter 812 includes one or more stages of analogintegrators.

FIG. 7 is a simplified timing diagram for the oscillator 808 withperiodic jittering as part of the amplification system 800 according toan embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. The waveform 702 represents an oscillation frequencyassociated with the clock signal 826 and/or a ramping frequencyassociated with the ramp signal 824 of the oscillator 808 as a functionof time. A jittering period T₀ that starts at t₀ and ends at t₈ is shownin FIG. 7. For example, t₀≤t₁≤t₂≤t₃≤t₄≤t₅≤t₆≤t₇≤t₈.

According to one embodiment, multiple frequency steps appear in thejittering period T₀, where each frequency step corresponds to aparticular oscillation frequency value or a particular ramping frequencyvalue. For example, between t₀ and t₁, the oscillation frequency or theramping frequency has a value of f₁. As an example, the oscillationfrequency or the ramping frequency increases to another value f₂ betweent₁ and t₂, and then increase to a value f₃ between t₃ and t₄. Between t₄and t₅, the oscillation frequency or the ramping frequency reaches apeak value f₄ within the jittering period T₀, according to certainembodiments. As an example, between t₅ and t₈, the oscillation frequencyor the ramping frequency decreases in value till the end of thejittering period T₀, and then a next jittering period begins. Forexample, the frequency values f₁, f₂, f₃, f₄, f₅, f₆, and f₇ appearduring the next jittering period again. In another example, a repeatrate of the frequency jittering (e.g., the repeating of the jitteringsequence) is inversely proportional to the jittering period T₀. In yetanother example, the repeat rate is larger in magnitude than an upperlimit of an audio frequency range (e.g., of about 20 Hz to about 20kHz). As an example, the frequency of the audio signal 830 is notaffected by the frequency jittering as shown in FIG. 7, according tosome embodiments.

FIG. 8(a) is a simplified diagram showing certain components of theoscillator 808 with periodic jittering as part of the amplificationsystem 800 according to one embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The oscillator 808 includesa jittering-sequence generator 902, current sources 904 and 906,switches 908 and 910, a transconductance amplifier 912, a capacitor 916,comparators 914 and 918, NAND gates 920 and 922, and a buffer 924.

According to one embodiment, the jittering-sequence generator 902receives the clock signal 826 and generates a signal 930 to trigger achange of a charging current 932 related to the current source 904and/or the discharging current 934 related to the current source 906.For example, the switch 908 is opened or closed in response to acharging signal 926, and the switch 910 is opened or closed in responseto a discharging signal 928. In one example, if the charging signal 926is at a logical high level, the discharging signal 928 is at a logic lowlevel, and if the charging signal 926 is at a logic low level, thedischarging signal 928 is at a logic high level. In another example, theclock signal 826 changes between the logic high level and the logic lowlevel similar to the discharging signal 928. For example, the clocksignal 826 is associated with one or more oscillation periodscorresponding to the oscillation frequency of the clock signal 826. Inanother example, the ramp signal 824 is associated with one or moreramping periods corresponding to the ramping frequency of the rampsignal 824. In yet another example, a switching period is equal induration to a ramping period. In yet another example, a switching periodand a ramping period start at a same time and end at a same time. In yetanother example, in a ramping period, the ramp signal 824 increases inmagnitude during a time period within the ramping period, and decreasesin magnitude during another time period within the ramping period.

According to another embodiment, the jittering-sequence generator 902detects a rising edge of the clock signal 826, and generates the signal930 to change the charging current 932 and/or the discharging current934 to jitter the frequency of the clock signal 826 and/or the rampingfrequency of the ramp signal 824. For example, the change of theoscillation frequency of the clock signal 826 and/or the rampingfrequency of the ramp signal 824 is determined by the magnitude of thecharging current 932 and/or the discharging current 934. In anotherexample, at the rising edge of the clock signal 826, the ramp signal 824reaches a peak magnitude during the ramping period. In yet anotherexample, the charging current 932 is equal in magnitude to thedischarging current 934. In yet another example, the current 932 and thecurrent 934 are equal in magnitude. In yet another example, a chargingperiod for charging the capacitor 916 is determined based on acomparison between the ramp signal 824 and a reference signal 998 (e.g.,V_(REF+)). In yet another example, a discharging period for dischargingthe capacitor 916 is determined based on a comparison between the rampsignal 824 and a reference signal 996 (e.g., V_(REF−)).

FIG. 8(b) is a simplified timing diagram for the oscillator 808 as shownin FIG. 8(a) as part of the amplification system 800 according to oneembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. One of ordinaryskill in the art would recognize many variations, alternatives, andmodifications. The waveform 1006 represents the clock signal 826 as afunction of time and the waveform 1008 represents the ramp signal 824 asa function of time. For example, t₉≤t₁₀≤t₁₁≤t₁₂≤t₁₃.

According to one embodiment, as shown in FIG. 8(b), during a firstramping period (e.g., T_(n)), the ramp signal 824 decreases from amagnitude 1018 (e.g., at t₉) to a magnitude 1020 (e.g., at t₁₀), andthen increases to a magnitude 1022 (e.g., at t₁₁). For example, duringthe ramping period (e.g., T_(n)), the charging current 932 and/or thedischarging current 934 keeps at a first magnitude within a particularrange (e.g., the range between a maximum magnitude and a minimummagnitude). At t₁₁, a second ramping period (e.g., T_(n+1)) begins, anda rising edge 1028 appears in the clock signal 826, according to someembodiments. For example, the jittering-sequence generator 902 outputsthe signal 930 to change the charging current 932 and/or the dischargingcurrent 934 to jitter the oscillation frequency of the clock signal 826and/or the ramping frequency of the ramp signal 824. In another example,a slope of the ramp signal 824 in the second ramping period (e.g.,T_(n+1)) becomes different from that in the first ramping period (e.g.,T_(n)) in response to the change of the charging current 932 and/or thedischarging current 934. In yet another example, the duration of thesecond ramping period (e.g., T_(n+1)) becomes different from that of thefirst ramping period (e.g., T_(n)) in response to the change of thecharging current 932 and/or the discharging current 934. In someembodiments, the change of the slope of the ramp signal 824 (e.g., aramp-up slope and/or a ramp-down slope) results in a change in theramping frequency associated with the ramp signal 824 and/or theoscillation frequency associated with the clock signal 826.

According to another embodiment, during the second ramping period (e.g.,T_(n+1)), the ramp signal 824 decreases from the magnitude 1022 (e.g.,at t₁₁) to a magnitude 1024 (e.g., at t₁₂), and then increases to amagnitude 1026 (e.g., at t₁₃). For example, during the second rampingperiod (e.g., T_(n+1)), the charging current 932 and/or the dischargingcurrent 934 keeps at a second magnitude within the range between themaximum magnitude and the minimum magnitude. In another example, thesecond magnitude is different from the first magnitude. At t₁₃, a thirdramping period (e.g., T_(n+2)) begins, and another rising edge 1030appears in the clock signal 826, according to some embodiments. Forexample, the jittering-sequence generator 902 changes the signal 930 tochange the charging current 932 and/or the discharging current 934 againto jitter the oscillation frequency of the clock signal 826 and/or theramping frequency of the ramp signal 824. In another example, a slope ofthe ramp signal 824 in the third ramping period (e.g., T_(n+2)) becomesdifferent from that in the second ramping period (e.g., T_(n+1)) inresponse to the change of the charging current 932 and/or thedischarging current 934. In yet another example, the duration of thethird ramping period (e.g., T_(n+2)) becomes different from that of thesecond ramping period (e.g., T_(n+1)) in response to the change of thecharging current 932 and/or the discharging current 934. In someembodiments, the change of the slope of the ramp signal 824 (e.g., aramp-up slope and/or a ramp-down slope) results in a change in theramping frequency associated with the ramp signal 824 and/or theoscillation frequency associated with the clock signal 826. For example,the magnitudes 1018, 1022 and 1026 of the ramp signal 824 are related tothe reference signal 998 (e.g., V_(REF+)), and the magnitudes 1020 and1024 of the ramp signal 824 are related to the reference signal 996(e.g., V_(REF−)).

FIG. 8(c) is a simplified diagram showing certain components of theoscillator 808 with periodic jittering as part of the amplificationsystem 800 according to another embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. The oscillator 808includes a current-controlled oscillation component 1410, an encoder1406, a current digital-analog converter (DAC) 1408, and a countercomponent 1404. For example, the counter component 1404, the encoder1406, and the current DAC 1408 are included in the jittering-sequencegenerator 902. In another example, a current DAC (e.g., the current DAC1408) is included in the current source 904 and/or the current source906. In yet another example, the current-controlled oscillationcomponent 1410 includes the current sources 904 and 906, the switches908 and 910, the capacitor 916, the amplifier 912, the comparators 914and 918, the NAND gates 920 and 922, and the buffer 928.

According to one embodiment, the counter component 1404 receives theclock signal 826 and generates a signal 1412 that is encoded by theencoder 1406. As an example, an encoded signal 1414 is received by theDAC 1408 which outputs a current signal 1416 (e.g., I_(dac2)) to thecurrent-controlled oscillation component 1410. In another example, thecurrent-controlled oscillation component 1410 also receives a currentsignal 1402 (e.g., I₀) and outputs the clock signal 826 and the rampsignal 824. As shown in FIG. 8(c), the counter component 1404 changesthe signal 1412 in response to the clock signal 826 to jitter theoscillation frequency of the clock signal 826 and/or the rampingfrequency of the ramp signal 824. For example, the clock signal 826 isassociated with one or more switching periods corresponding to theoscillation frequency of the clock signal 826. In another example, theramp signal 824 is associated with one or more ramping periodscorresponding to the ramping frequency of the ramp signal 824. In yetanother example, a switching period is equal in duration to a rampingperiod. In yet another example, a switching period and a ramping periodstart at a same time and end at a same time. In yet another example, thecurrent signal 1402 is fixed.

According to another embodiment, at the beginning of a first switchingperiod, the counter component 1404 generates the signal 1412 at a firstvalue, and the current DAC 1408 generates the current 1416 at a firstmagnitude in response to the signal 1412 being at the first value. Forexample, the oscillation frequency of the clock signal 826 and/or theramping frequency of the ramp signal 824 is jittered in response to thecurrent 1416 being at the first magnitude. In another example, at thebeginning of a second switching period that follows the first switchingperiod, the counter component 1404 generates the signal 1412 at a secondvalue, and the current DAC 1408 generates the current 1416 at a secondmagnitude in response to the signal 1412 being at the second value. Inyet another example, the oscillation frequency of the clock signal 826and/or the ramping frequency of the ramp signal 824 is jittered again inresponse to the current 1416 being at the second magnitude.

According to yet another embodiment, the ramping frequency of the rampsignal 824 is determined as follows:

$\begin{matrix}{f = \frac{\beta}{I_{0} + I_{{dac}\; 2}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

where β represents a constant, I₀ represents the direct-current signal1402, and I_(dac2) represents the signal 1416.

If I_(dac2)<<I₀, the ramping frequency of the ramp signal 824 isdetermined as follows, according to certain embodiments:

$\begin{matrix}{f = {\frac{\beta}{I_{0}}\left( {1 - \frac{I_{{dac}\; 2}}{I_{0}}} \right)}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

Based on Equation 2, the ramping frequency of the ramp signal 824 ismodulated by the current signal 1416. For example, the charging current932 and the discharging current 934 satisfy the following equation:

I _(charge) =I _(discharge) =I ₀ +I _(dac2)   (Equation 3)

According to yet another embodiment, if no input signals are received bythe amplification system 800, a modulation period associated with theoutput signal 820 (e.g., PWM) is determined as follows:

$\begin{matrix}{T_{i,{PWM}} = {{\frac{1}{4} \times T_{{i - 1},{RAMP}}} + {\frac{3}{4} \times T_{i,{RAMP}}}}} & \left( {{Equation}\mspace{11mu} 4} \right)\end{matrix}$

where T_(i,PWM) represents a current modulation period associated withthe output signal 820, T_(i-1,RAMP) represents a previous rampingperiod, and T_(i,RAMP) represents a current ramping period.

According to yet another embodiment, if the amplification system 800receives one or more input signals, the duty cycle of the output signal820 changes, and the modulation period associated with the output signal820 is determined as follows:

$\begin{matrix}{T_{i,{PWM}} = {{\frac{1}{\alpha} \times T_{{i - 1},{RAMP}}} + {\frac{\alpha - 1}{\alpha} \times T_{i,{RAMP}}}}} & \left( {{Equation}\mspace{14mu} 5} \right)\end{matrix}$

where α represents a positive number associated with the input signals.Based on Equation 5, if α changes with the increasing input signals, theduty cycle of the output signal 820 increases, and more frequency valuesfor the output signal 820 appear, according to some embodiments.

FIG. 9 is a simplified timing diagram for the amplification system 800that includes the oscillator 808 with periodic jittering and receivesthe input signal 818 according to one embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. The waveform1102 represents values of a modulation frequency associated with thesignal 820 (e.g., PWM) of the amplification system 800 as a function oftime. For example, the amplification system 800 includes the oscillator808 with periodic jittering as shown in FIG. 7, FIG. 8(a), FIG. 8(b),and/or FIG. 8(c).

As shown in FIG. 9, there are two jittering periods T₁ and T_(m).According to one embodiment, multiple frequency steps appear in each ofthe jittering periods T₁ and T_(m), where each frequency stepcorresponds to a particular switching frequency value. But the frequencyvalues of the jittering period T₁ are different from those of thejittering period T_(m), and further, the frequency values appearing inthe jittering periods T₁ and T_(m) are different from the frequencyvalues in other jittering periods, as shown in FIG. 9, in certainembodiments. Compared with FIG. 7, more frequency values appear overtime due to the jittering of the ramping signal 824 by changing thecharging current 932 and the discharging current 934, according to someembodiments.

As discussed above and further emphasized here, FIG. 7, FIG. 8(a), FIG.8(b), FIG. 8(c) and FIG. 9 are merely examples, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. In certainembodiments, the jittering-sequence generator 902 is external to theoscillator 808. In some embodiments, the counter component 1404, theencoder 1406, and the current DAC 1408 are external to the oscillator808. For example, FIG. 7 and FIG. 9 show periodic jittering, but theperiodic jittering can be combined with pseudo-random jittering, asshown in FIG. 10.

FIG. 10 is a simplified frequency spectrum diagram showing a combinationof periodic jittering and pseudo-random jittering for the oscillator 808as part of the amplification system 800 according to yet anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. One of ordinaryskill in the art would recognize many variations, alternatives, andmodifications.

According to one embodiment, an audio frequency range is between afrequency value f_(c1) (e.g., about 20 Hz) and a frequency value f_(c2)(e.g., about 20 kHz), and an oscillation frequency of the clock signal826 (e.g., f_(osc)) is larger in magnitude than the upper limit of theaudio frequency range. As an example, a frequency (e.g., f_(j1))associated with the periodic jittering as shown in FIG. 7 and/or FIG. 9is larger in magnitude than the upper limit of the audio frequencyrange. In another example, a frequency (e.g., f_(j2)) associated with apseudo-random jittering is smaller in magnitude than a lower limit ofthe audio frequency range. The frequency components of the audio signals830 is not affected by the periodic jittering and/or the pseudo-randomjittering, according to certain embodiments. According to anotherembodiment, if the number of frequency values for the periodic jitteringis N_(j1) and the number of frequency values for the pseudo-randomjittering is N_(j2), the number of frequency values associated with theoutput signals 820 without any input signals is determined as follows:

N _(total) =N _(j1) ×N _(j2)   (Equation 6)

where N_(total) represents the number of frequency values associatedwith the output signals 820. For example, if N_(j1)=7 and N_(j2)=16,N_(total)=112. If the amplification system 800 receives input signals,more frequency values appear, as shown in FIG. 10, according to certainembodiments.

FIG. 11 is a simplified frequency spectrum diagram for the amplificationsystem 800 that includes the oscillator 808 with a combination ofperiodic jittering and pseudo-random jittering if the input signal 818is zero according to one embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The waveform 1202represents magnitudes associated with the signal 820 (e.g., PWM) of theamplification system 800 as a function of frequency.

FIG. 12(a) is a simplified diagram showing certain components of theoscillator 808 with a combination of periodic jittering andpseudo-random jittering as part of the amplification system 800according to one embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The oscillator 808 includesa jittering-sequence generator 1502, current sources 1504 and 1506,switches 1508 and 1510, a transconductance amplifier 1512, a capacitor1516, comparators 1514 and 1518, NAND gates 1520 and 1522, and a buffer1524.

According to one embodiment, the jittering-sequence generator 1502receives the clock signal 826 and generates a signal 1530 to trigger achange of a charging current 1532 related to the current source 1504and/or a discharging current 1534 related to the current source 1506 toprovide a combination of periodic jittering and pseudo-random jitteringto the oscillation frequency of the clock signal 826 and/or the rampingfrequency of the ramp signal 824. For example, the switch 1508 is openedor closed in response to a charging signal 1526, and the switch 1510 isopened or closed in response to a discharging signal 1528. In oneexample, if the charging signal 1526 is at a logical high level, thedischarging signal 1528 is at a logic low level, and if the chargingsignal 1526 is at a logic low level, the discharging signal 1528 is at alogic high level. In another example, the clock signal 826 changesbetween the logic high level and the logic low level similar to thedischarging signal 1528.

FIG. 12(b) is a simplified diagram showing certain components of theoscillator 808 with a combination of periodic jittering andpseudo-random jittering as part of the amplification system 800according to another embodiment of the present invention. This diagramis merely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The oscillator 808 includesa current-controlled oscillation component 1302, alinear-feedback-shift-register (LFSR) component 1304, encoder components1306 and 1312, current digital-analog converters (DACs) 1308 and 1314,and a counter component 1310. For example, the counter component 1310,the encoder component 1312, the current DAC 1314, the LFSR 1304, theencoder component 1306 and the current DAC 1308 are included in thejittering-sequence generator 1502. In another example, a current DAC(e.g., the current DAC 1308 or the current DAC 1314) is included in thecurrent source 1504 and/or the current source 1506. In yet anotherexample, the current-controlled oscillation component 1302 includes thecurrent sources 1504 and 1506, the switches 1508 and 1510, the capacitor1516, the amplifier 1512, the comparators 1514 and 1518, the NAND gates1520 and 1522, and the buffer 1528.

According to one embodiment, the LFSR component 1304 that is implementedfor pseudo-random jittering receives the clock signal 826 and generatesa signal 1322 that is encoded by the encoder component 1306. Forexample, an encoded signal 1324 is received by the DAC 1308 whichoutputs a current signal 1318 (e.g., I_(dac1)) to the current-controlledoscillation component 1302. In another example, the counter component1310 that is implemented for periodic jittering receives the clocksignal 826 and generates a signal 1326 that is encoded by the encoder1312. As an example, an encoded signal 1328 is received by the DAC 1314which outputs a current signal 1320 (e.g., I_(dac2)) to thecurrent-controlled oscillation component 1302. In another example, thecurrent-controlled oscillation component 1302 also receives a currentsignal 1316 (e.g., I₀) and outputs the clock signal 826 and the rampsignal 824. In another example, the current signal 1316 is fixed.

According to another embodiment, the ramping frequency of the rampsignal 824 is determined as follows:

$\begin{matrix}{f = \frac{\beta}{I_{0} + I_{{dac}\; 1} + I_{{dac}\; 2}}} & \left( {{Equation}\mspace{14mu} 7} \right)\end{matrix}$

where β represents a constant, I₀ represents the signal 1316, I_(dac1)represents the signal 1318, and I_(dac2) represents the signal 1320.

If I_(dac1)+I_(dac2)<<I₀, the ramping frequency of the ramp signal 824is determined as follows, according to certain embodiments:

$\begin{matrix}{f = {\frac{\beta}{I_{0}}\left( {1 - \frac{I_{{dac}\; 1} + I_{{dac}\; 2}}{I_{0}}} \right)}} & \left( {{Equation}\mspace{14mu} 8} \right)\end{matrix}$

Based on Equation 8, the ramping frequency of the ramp signal 824 ismodulated by the current signals 1318 and 1320. For example, thecharging current 932 and the discharging current 934 satisfy thefollowing equation:

|I _(charge) |=|I _(discharge) |=|I ₀ +I _(dac1) +I _(dac2)|  (Equation9)

As discussed above and further emphasized here, FIG. 12(a) and FIG.12(b) are merely examples, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. In certain embodiments, thejittering-sequence generator 1502 is external to the oscillator 808. Insome embodiments, the counter component 1504, the encoder 1506, and thecurrent DAC 1508 are external to the oscillator 808.

According to one embodiment, a system for amplifying multiple inputsignals to generate multiple output signals includes a first channel, asecond channel, and a third channel. The first channel is configured toreceive one or more first input signals, process information associatedwith the one or more first input signals and a first ramp signal, andgenerate one or more first output signals based on at least informationassociated with the one or more first input signals and the first rampsignal. The second channel is configured to receive one or more secondinput signals, process information associated with the one or moresecond input signals and a second ramp signal, and generate one or moresecond output signals based on at least information associated with theone or more second input signals and the second ramp signal. The thirdchannel is configured to receive one or more third input signals,process information associated with the one or more third input signalsand a third ramp signal, and generate one or more third output signalsbased on at least information associated with the one or more thirdinput signals and the third ramp signal. The first ramp signalcorresponds to a first phase. The second ramp signal corresponds to asecond phase. The first phase and the second phase are different. Forexample, the system is implemented according to at least FIG. 3, and/orFIG. 4.

According to another embodiment, a system for amplifying multiple inputsignals to generate multiple output signals includes a first channel anda second channel. The first channel is configured to receive one or morefirst input signals, process information associated with the one or morefirst input signals and a first ramp signal, and generate one or morefirst output signals based on at least information associated with theone or more first input signals and the first ramp signal. The secondchannel is configured to receive one or more second input signals,process information associated with the one or more second input signalsand a second ramp signal, and generate one or more second output signalsbased on at least information associated with the one or more secondinput signals and the second ramp signal. The first ramp signalcorresponds to a first phase. The second ramp signal corresponds to asecond phase. A difference between the first phase and the second phaseis equal to 180 degrees. For example, the system is implementedaccording to at least FIG. 5(a).

According to yet another embodiment, a system for amplifying multipleinput signals to generate multiple output signals includes a firstchannel and a second channel. The first channel includes a first loopfilter, a first signal processing component and a first outputcomponent, and is configured to receive one or more first input signals,process information associated with the one or more first input signalsand a ramp signal, and generate one or more first output signals basedon at least information associated with the one or more first inputsignals and the ramp signal. The second channel includes a second loopfilter, a second signal processing component and a second outputcomponent, and is configured to receive one or more second inputsignals, process information associated with the one or more secondinput signals and the ramp signal, and generate one or more secondoutput signals based on at least information associated with the one ormore second input signals and the ramp signal. The first loop filter isconfigured to process information associated with the one or more firstinput signals and generate one or more first filtered signals based onat least information associated with the one or more first inputsignals. The first signal processing component is configured to processinformation associated with the one or more first filtered signals andgenerate one or more first processed signals based on at leastinformation associated with the one or more first filtered signals. Thefirst output component is configured to process information associatedwith the one or more first processed signals and generate the one ormore first output signals based on at least information associate withthe one or more first processed signals. The second loop filter isconfigured to process the one or more second input signals and generateone or more second filtered signals based on at least informationassociated with the one or more second input signals. The second signalprocessing component is configured to process information associatedwith the one or more second filtered signals and generate one or moresecond processed signals based on at least information associated withthe one or more second filtered signals. The second output component isconfigured to process information associated with the one or more secondprocessed signals and generate the one or more second output signalsbased on at least information associate with the one or more secondprocessed signals. The one or more first processed signals areassociated with a first phase. The one or more second processed signalsare associated with a second phase. A difference between the first phaseand the second phase is equal to 180 degrees. For example, the system isimplemented according to at least FIG. 5(b).

In one embodiment, a system for amplifying multiple input signals togenerate multiple output signals includes a first channel and a secondchannel. The first channel includes a first loop filter and one or morefirst comparators, and is configured to receive one or more first inputsignals, process information associated with the one or more first inputsignals and a ramp signal, and generate one or more first output signalsbased on at least information associated with the one or more firstinput signals and the ramp signal. The second channel includes a secondloop filter and one or more second comparators, and is configured toreceive one or more second input signals, process information associatedwith the one or more second input signals and the ramp signal, andgenerate one or more second output signals based on at least informationassociated with the one or more second input signals and the rampsignal. The first loop filter is configured to process informationassociated with the one or more first input signals and generate one ormore first filtered signals based on at least information associatedwith the one or more first input signals. The one or more firstcomparators include one or more first terminals and one or more secondterminals and are configured to receive the one or more first filteredsignals at the first terminals and the ramp signal at the secondterminals, generate one or more first comparison signals based on atleast information associated with the first filtered signals and theramp signal, and output the one or more first comparison signals inorder to generate the one or more first output signals. The second loopfilter is configured to process information associated with the one ormore second input signals and generate one or more second filteredsignals based on at least information associated with the one or moresecond input signals. The one or more second comparators include one ormore third terminals and one or more fourth terminals and are configuredto receive the one or more second filtered signals at the thirdterminals and the ramp signal at the fourth terminals, generate one ormore second comparison signals based on at least information associatedwith the second filtered signals and the ramp signal, and output the oneor more second comparison signals in order to generate the one or moresecond output signals. The one or more second terminals include one ormore inverting terminals and the one or more fourth terminals includeone or more non-inverting terminals, or the one or more second terminalsinclude one or more non-inverting terminals and the one or more fourthterminals include one or more inverting terminals. For example, thesystem is implemented according to at least FIG. 5(c).

In another embodiment, a system for amplifying one or more input signalsto generate one or more output signals includes, an oscillator componentconfigured to generate a ramp signal associated with a rampingfrequency, a loop filter component configured to receive one or moreinput signals and generate one or more filtered signals based on atleast information associated with the one or more input signals, and acomparator component configured to receive the one or more filteredsignals and the ramp signal and generate one or more comparison signalsbased on at least information associated with the one or more filteredsignals and the ramp signal. The oscillator component is furtherconfigured to, change the ramping frequency periodically so that one ormore changes in the ramping frequency are made in each jittering periodcorresponding to a jittering frequency, and output the ramping signalassociated with the changed ramping frequency. The jittering frequencyis larger than an upper limit of a predetermined audio frequency range.For example, the system is implemented according to at least FIG. 6,FIG. 7, FIG. 8(a), FIG. 8(b), FIG. 8(c), and/or FIG. 9.

In yet another embodiment, a system for amplifying one or more inputsignals to generate one or more output signals includes, an oscillatorcomponent configured to generate a ramp signal associated with a rampingfrequency, the ramping frequency corresponding to one or more rampingperiods, a loop filter component configured to receive one or more inputsignals and generate one or more filtered signals based on at leastinformation associated with the one or more input signals, and acomparator component configured to receive the one or more filteredsignals and the ramp signal and generate one or more comparison signalsbased on at least information associated with the one or more filteredsignals and the ramp signal. The oscillator component is furtherconfigured to, at an end of a first ramping period, change a chargingcurrent or a discharging current so that a first duration of the firstramping period differs from a second duration of a second ramping periodfollowing the first ramping period. The first duration and the secondduration correspond to different magnitudes of the ramping frequency.For example, the system is implemented according to at least FIG. 6,FIG. 7, FIG. 8(a), FIG. 8(b), FIG. 8(c), FIG. 9, FIG. 10, FIG. 11, FIG.12(a), and/or FIG. 12(b).

According one embodiment, a method for amplifying multiple input signalsto generate multiple output signals includes, receiving one or morefirst input signals, processing information associated with the one ormore first input signals and a first ramp signal, and generating one ormore first output signals based on at least information associated withthe one or more first input signals and the first ramp signal. Themethod further includes, receiving one or more second input signals,processing information associated with the one or more second inputsignals and a second ramp signal, and generating one or more secondoutput signals based on at least information associated with the one ormore second input signals and the second ramp signal. In addition, themethod includes receiving one or more third input signals, processinginformation associated with the one or more third input signals and athird ramp signal, and generating one or more third output signals basedon at least information associated with the one or more third inputsignals and the third ramp signal. The first ramp signal corresponds toa first phase. The second ramp signal corresponds to a second phase. Thefirst phase and the second phase are different. For example, the methodis implemented according to at least FIG. 3, and/or FIG. 4.

According to another embodiment, a method for amplifying multiple inputsignals to generate multiple output signals includes, receiving one ormore first input signals, processing information associated with the oneor more first input signals and a first ramp signal, and generating oneor more first output signals based on at least information associatedwith the one or more first input signals and the first ramp signal. Themethod further includes, receiving one or more second input signals,processing information associated with the one or more second inputsignals and a second ramp signal, and generating one or more secondoutput signals based on at least information associated with the one ormore second input signals and the second ramp signal. The first rampsignal corresponds to a first phase. The second ramp signal correspondsto a second phase. A difference between the first phase and the secondphase is equal to 180 degrees. For example, the method is implementedaccording to at least FIG. 5(a).

According to yet another embodiment, a method for amplifying multipleinput signals to generate multiple output signals includes, receivingone or more first input signals by a first channel including a firstloop filter, a first signal processing component and a first outputcomponent, processing information associated with the one or more firstinput signals and a ramp signal, and generating one or more first outputsignals based on at least information associated with the one or morefirst input signals and the ramp signal. The method further includes,receiving one or more second input signals by a second channel includinga second loop filter, a second signal processing component and a secondoutput component, processing information associated with the one or moresecond input signals and the ramp signal, and generating one or moresecond output signals based on at least information associated with theone or more second input signals and the ramp signal. The processinginformation associated with the one or more first input signals and aramp signal includes, processing information associated with the one ormore first input signals by the first loop filter, generating one ormore first filtered signals based on at least information associatedwith the one or more first input signals, processing informationassociated with the one or more first filtered signals by the firstsignal processing component, and generating one or more first processedsignals based on at least information associated with the one or morefirst filtered signals. The generating one or more first output signalsbased on at least information associated with the one or more firstinput signals and the ramp signal includes, processing informationassociated with the one or more first processed signals by the firstoutput component, and generating the one or more first output signalsbased on at least information associate with the one or more firstprocessed signals. The processing information associated with the one ormore second input signals and the ramp signal includes, processinginformation associated with the one or more second input signals by thesecond loop filter, generating one or more second filtered signals basedon at least information associated with the one or more second inputsignals, processing information associated with the one or more secondfiltered signals by the second signal processing component, andgenerating one or more second processed signals based on at leastinformation associated with the one or more second filtered signals. Thegenerating one or more second output signals based on at leastinformation associated with the one or more second input signals and theramp signal includes, processing information associated with the one ormore second processed signals by the second output component, andgenerating the one or more second output signals based on at leastinformation associate with the one or more second processed signals. Theone or more first processed signals are associated with a first phase,the one or more second processed signals are associated with a secondphase, and a difference between the first phase and the second phase isequal to 180 degrees. For example, the method is implemented accordingto at least FIG. 5(b).

In one embodiment, a method for amplifying multiple input signals togenerate multiple output signals includes, receiving one or more firstinput signals by a first channel including a first loop filter and oneor more first comparators, processing information associated with theone or more first input signals and a ramp signal, and generating one ormore first output signals based on at least information associated withthe one or more first input signals and the ramp signal. The methodfurther includes, receiving one or more second input signals by a secondchannel including a second loop filter and one or more secondcomparators, processing information associated with the one or moresecond input signals and the ramp signal, and generating one or moresecond output signals based on at least information associated with theone or more second input signals and the ramp signal. The processinginformation associated with the one or more first input signals and aramp signal includes, processing information associated with the one ormore first input signals at the first loop filter, and generating one ormore first filtered signals based on at least information associatedwith the one or more first input signals. The generating one or morefirst output signals based on at least information associated with theone or more first input signals and the ramp signal includes, receivingthe one or more first filtered signals by one or more first terminals ofthe one or more first comparators, receiving the ramp signal by one ormore second terminals of the one or more first comparators, generatingone or more first comparison signals based on at least informationassociated with the first filtered signals and the ramp signal,outputting the one or more first comparison signals, and generating theone or more first output signals based on at least informationassociated with the one or more first comparison signals. The processinginformation associated with the one or more second input signals and theramp signal includes, processing information associated with the one ormore second input signals by the second loop filter, and generating oneor more second filtered signals based on at least information associatedwith the one or more second input signals. The generating one or moresecond output signals based on at least information associated with theone or more second input signals and the ramp signal includes, receivingthe one or more second filtered signals by one or more third terminalsof the one or more second comparators, receiving the ramp signal by oneor more fourth terminals of the one or more second comparators,generating one or more second comparison signals based on at leastinformation associated with the second filtered signals and the rampsignal, outputting the one or more second comparison signals, andgenerating the one or more second output signals based on at leastinformation associated with the one or more second comparison signals.The one or more second terminals include one or more inverting terminalsand the one or more fourth terminals include one or more non-invertingterminals, or the one or more second terminals include one or morenon-inverting terminals and the one or more fourth terminals include oneor more inverting terminals. For example, the method is implementedaccording to at least FIG. 5(c).

In another embodiment, a method for amplifying one or more input signalsto generate one or more output signals includes, generating a rampsignal associated with a ramping frequency, receiving one or more inputsignals, and processing information associated with the one or moreinput signals. The method further includes, generating one or morefiltered signals based on at least information associated with the oneor more input signals, receiving the one or more filtered signals andthe ramp signal, processing information associated with the one or morefiltered signals and the ramp signal, and generating one or morecomparison signals based on at least information associated with the oneor more filtered signals and the ramp signal. The generating a rampsignal associated with a ramping frequency includes, changing theramping frequency periodically so that one or more changes in theramping frequency are made in each jittering period corresponding to ajittering frequency, and outputting the ramping signal associated withthe changed ramping frequency. The jittering frequency is larger than anupper limit of a predetermined audio frequency range. For example, themethod is implemented according to at least FIG. 6, FIG. 7, FIG. 8(a),FIG. 8(b), FIG. 8(c), and/or FIG. 9.

In yet another embodiment, a method for amplifying one or more inputsignals to generate one or more output signals includes, generating aramp signal associated with a ramping frequency, the ramping frequencycorresponding to one or more ramping periods, receiving one or moreinput signals, and processing information associated with the one ormore input signals. The method further includes, generating one or morefiltered signals based on at least information associated with the oneor more input signals, receiving the one or more filtered signals andthe ramp signal, and generating one or more comparison signals based onat least information associated with the one or more filtered signalsand the ramp signal. The generating a ramp signal associated with aramping frequency includes changing a charging current or a dischargingcurrent at an end of a first ramping period so that a first duration ofthe first ramping period differs from a second duration of a secondramping period following the first ramping period. The first durationand the second duration correspond to different magnitudes of theramping frequency. For example, the method is implemented according toat least FIG. 6, FIG. 7, FIG. 8(a), FIG. 8(b), FIG. 8(c), FIG. 9, FIG.10, FIG. 11, FIG. 12(a), and/or FIG. 12(b).

For example, some or all components of various embodiments of thepresent invention each are, individually and/or in combination with atleast another component, implemented using one or more softwarecomponents, one or more hardware components, and/or one or morecombinations of software and hardware components. In another example,some or all components of various embodiments of the present inventioneach are, individually and/or in combination with at least anothercomponent, implemented in one or more circuits, such as one or moreanalog circuits and/or one or more digital circuits. In yet anotherexample, various embodiments and/or examples of the present inventioncan be combined.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

1-53. (canceled)
 54. A system for amplifying one or more input signalsto generate one or more output signals, the system comprising: anoscillator configured to generate a ramp signal associated with aramping frequency; and a comparator configured to receive the rampsignal and generate one or more comparison signals based at least inpart on the ramp signal; wherein the oscillator is further configuredto: change the ramping frequency pseudo-randomly so that one or morechanges in the ramping frequency are made in a pseudo-random-jitteringperiod corresponding to a pseudo-random-jittering frequency; and whereinthe pseudo-random-jittering frequency is smaller than a lower limit of apredetermined audio frequency range.
 55. The system of claim 54 whereinthe predetermined audio frequency range includes an upper limit of 20kHz and a lower limit of 20 Hz.
 56. The system of claim 54 wherein theoscillator is further configured to, during a specificpseudo-random-jittering period, change the ramping frequency amongmultiple frequency values.
 57. The system of claim 54 wherein theoscillator includes: a first current source configured to provide adischarging current; a second current source configured to provide acharging current; a capacitor configured to be charged in response tothe charging current and be discharged in response to the dischargingcurrent, the ramp signal being associated with a voltage related to thecapacitor; a transconductance amplifier configured to receive an inputcurrent associated with the charging current or the discharging currentand output the ramp signal based on at least information associated withthe input current; and a jittering-sequence generator configured tochange the charging current and the discharging current periodically sothat one or more changes in the charging current and the dischargingcurrent are made in a corresponding jittering period; wherein thetransconductance amplifier is further configured to increase the rampsignal in magnitude in response to the capacitor being charged anddecrease the ramp signal in magnitude in response to the capacitor beingdischarged.
 58. The system of claim 57 wherein the oscillator furtherincludes: a first comparator configured to receive the ramp signal and afirst reference signal and output a first comparison signal based on atleast information associated with the ramp signal and the firstreference signal; a second comparator configured to receive the rampsignal and a second reference signal and output a second comparisonsignal based on at least information associated with the ramp signal andthe second reference signal; and a signal processor configured toreceive the first comparison signal and the second comparison signal andgenerate a discharge signal and a charge signal based on at leastinformation associated with the first comparison signal and the secondcomparison signal; wherein: the capacitor is further configured to becharged in response to the charge signal and be discharged in responseto the discharge signal; and the jittering-sequence generator is furtherconfigured to receive a clock signal associated with the dischargesignal, the clock signal being related to the ramping frequency.
 58. Thesystem of claim 54 wherein the oscillator includes: a shift-registerconfigured to receive a clock signal associated with the rampingfrequency and generate a register signal based on at least informationassociated with the clock signal; an encoder configured to receive theregister signal and generate a coding signal based on at leastinformation associated with the register signal; a currentdigital-to-analog converter configured to receive the coding signal andgenerate a jittering current based on at least information associatedwith the coding signal; and a current-controlled oscillator configuredto receive a first current and the jittering current and output theclock signal and the ramp signal based on at least informationassociated with the first current and the jittering current; wherein thejittering current is related to the one or more changes in the rampingfrequency made in a corresponding pseudo-random-jittering period.
 59. Asystem for amplifying one or more input signals to generate one or moreoutput signals, the system comprising: an oscillator configured togenerate a ramp signal associated with a ramping frequency; and acomparator configured to receive the ramp signal and generate one ormore comparison signals based at least in part on the ramp signal;wherein the oscillator includes: a first current source configured toprovide a discharging current; a second current source configured toprovide a charging current; a capacitor configured to be charged inresponse to the charging current and be discharged in response to thedischarging current, the ramp signal being associated with a voltagerelated to the capacitor; a transconductance amplifier configured toreceive an input current associated with the charging current or thedischarging current and output the ramp signal based on at leastinformation associated with the input current; and a jittering-sequencegenerator configured to change the charging current and the dischargingcurrent periodically so that one or more changes in the charging currentand the discharging current are made in a corresponding jitteringperiod; wherein the transconductance amplifier is further configured toincrease the ramp signal in magnitude in response to the capacitor beingcharged and decrease the ramp signal in magnitude in response to thecapacitor being discharged.
 60. The system of claim 59 wherein theoscillator is further configured to: change the ramping frequencypseudo-randomly so that one or more changes in the ramping frequency aremade in a pseudo-random-jittering period corresponding to apseudo-random-jittering frequency; and wherein thepseudo-random-jittering frequency is smaller than a lower limit of apredetermined audio frequency range.
 61. The system of claim 60 whereinthe predetermined audio frequency range includes an upper limit of 20kHz and a lower limit of 20 Hz.
 62. The system of claim 60 wherein theoscillator is further configured to, during a specificpseudo-random-jittering period, change the ramping frequency amongmultiple frequency values.
 63. The system of claim 59 wherein theoscillator further includes: a first comparator configured to receivethe ramp signal and a first reference signal and output a firstcomparison signal based on at least information associated with the rampsignal and the first reference signal; a second comparator configured toreceive the ramp signal and a second reference signal and output asecond comparison signal based on at least information associated withthe ramp signal and the second reference signal; and a signal processorconfigured to receive the first comparison signal and the secondcomparison signal and generate a discharge signal and a charge signalbased on at least information associated with the first comparisonsignal and the second comparison signal; wherein: the capacitor isfurther configured to be charged in response to the charge signal and bedischarged in response to the discharge signal; and thejittering-sequence generator is further configured to receive a clocksignal associated with the discharge signal, the clock signal beingrelated to the ramping frequency.
 64. The system of claim 60 wherein theoscillator further includes: a shift-register configured to receive aclock signal associated with the ramping frequency and generate aregister signal based on at least information associated with the clocksignal; an encoder configured to receive the register signal andgenerate a coding signal based on at least information associated withthe register signal; a current digital-to-analog converter configured toreceive the coding signal and generate a jittering current based on atleast information associated with the coding signal; and acurrent-controlled oscillator configured to receive a first current andthe jittering current and output the clock signal and the ramp signalbased on at least information associated with the first current and thejittering current; wherein the jittering current is related to the oneor more changes in the ramping frequency made in a correspondingpseudo-random-jittering period.